Papilloma viruses are a family with considerably more than 80 genotypes. Infection with papilloma viruses can lead to warts, papillomas, acanthomas, and skin and cervical carcinomas. A single illness can be caused by various papilloma virus types.
The capsids of the individual types of human pathogenic papilloma viruses (HPV) differ in their antigen characteristics (epitopes), meaning that after immunization with a specific HPV type, neutralizing antibodies cannot be induced against capsids of other HPV types. However, such antibodies would be necessary to give comprehensive protection against diseases that can be caused by different HPV types.
An example is that infection with one of more than ten different HPV types can lead to cervical cancer. Although the virus particles of the individual types are very similar in their composition, they carry different neutralizing epitopes on their surface and are therefore only recognized by the immune system if there has been either a previous natural infection or vaccination with particles of the same type, and type-specific (neutralizing) antibodies are induced.
Vaccines for the effective prevention of diseases caused by HPV should therefore contain a mixture of various virus types in order to give comprehensive protection. The production of such vaccines is, however, rendered more difficult owing to the fact described above, namely that one and the same disease can be caused by different HPV types.
To date only monovalent HPV vaccines have been developed, in other words vaccines directed against only one HPV type. However these have the serious disadvantage that they only guarantee protection against this one special HPV type, and not against other HPV types. Thus, monovalent HPV vaccines do not furnish a comprehensive immune reaction. Moreover, the production of conventional vaccines against HPV typically requires the production and purification of L1.